Cyclopentadiene is present to the extent of about 15% in the naphtha cracker C.sub.5 by-products stream from ethylene plants. One way to dispose of the C.sub.5 by-products stream is to use it as a fuel stock; a better use is as a source of petrochemicals. The most sought-after component of the C.sub.5 by-products stream is isoprene, which is also present at about 15% level. With the soaring price of natural rubber, pressure is mounting to expand synthetic polyisoprene production. For every pound of extract isoprene capacity that comes on stream, there will be a pound of cyclopentadiene. Thus, it stands to reason that with the sharp rise in the cost of crude oil, ethylene producers will have a strong incentive to find the most profitable uses for the by-products. In this context, cyclopentadiene is high on the list since its removal from the C.sub.5 stream is easily accomplished at the first step of the C.sub.5 purification process.
It is, therefore, desirable to promote reactions involving cyclopentadiene and derivatives thereof to produce useful products.